I/O is an acronym for Input/Output, which refers to the mechanism or process for the transfer of information between one system or component and another.

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Moving a file to a file that is being read

When a file is moved and the destination file already exists and is currently being read, will the operation succeed? Will it depend on how long the reading operation on the destination file lasts?
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77 views

I/O brings a machine to its knees [closed]

Why, on every Linux I've used, when a program is really I/O bound, it bogs the machine down? It just happened when I (accidentally) tried to make gcc compile a (valid!) 50Mb C file. GCC was so I/O ...
4
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3answers
129 views

Disallow File IO for a process except for FIFOs

How do you start a process that cannot do any file IO (opening / closing files, creating / deleting files, reading / writing files, etc.), except to read and write to pre-created FIFOs? (chroot will ...
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1answer
335 views

best programming language for I/O intensive tasks [closed]

I need to process "big data" (nearly 1TB which can be partitioned into smaller chunks). Consider several programming languages (Java, Python, C++, Perl) and other scripting options (Perl, awk, sed, ...
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1answer
1k views

`unbuffer` or `stdbuf` for removing stdout buffering?

Is there a difference between unbuffer(1) and stdbuf(1)? From what I gather, unbuffer makes more than the "best effort" of calling the libc function set(X)buf at the beginning, and then letting things ...
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2answers
2k views

How I/O channels are implemented in Linux kernel?

stdin, stdout, stderr are some integers that index into a data structure which 'knows' which I/O channels are to be used for the process. I understand this data structure is unique to every process. ...
4
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1answer
477 views

Execution time and resources after processes that has been running for so long

This might be a basic question, but I am getting hard time finding an answer to it. I am using RHEL6. After running any process that takes significant cpu time, I get a line that tells (I guess) the ...
6
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2answers
2k views

Massive, unpredictable I/O performance drop in Linux

I'm using Debian testing without any problems for ~6 years (I'm just regularly updating it), but recently it started to show a random behaviour that can be summarized as "Low I/O performance which ...
2
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1answer
77 views

Getting IO privileges in Linux

I have installed flashrom software. When i try to run sudo flashrom command it gives me "Could not get I/O privileges (Operation not permitted). You need to be root" error. Also I tried su command to ...
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0answers
291 views

How different is I/O handling of hard disk in AIX and Redhat Linux?

I am running a hadoop I/O workload in redhat linux and have ran that in IBM AIX as well with same underlying hardware, disk and disk configuration. With the default settings on the os redhat linux is ...
0
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2answers
477 views

IO utilization for /dev/null redirection?

I always use nohup to start my system. However, the output to nohup is so big that I'm thinking to redirect it to /dev/null. My concern is, will redirecting to /dev/null also incur some I/O operations ...
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1answer
3k views

How to measure total disk I/O per hour

I have a cloud server were we get billed also for disk IO usage. Here is an example from the stats: 04/Sep/2013 07:24:19 04/Sep/2013 08:24:19 0,5 GB / 1 vCPU (0,08 Kr. per hour): Charge for ...
2
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1answer
120 views

Why don't I see a file being copied right away with ls?

Is it due to the buffering in memory? I did cp /network/large_file . & and I kept doing ls -lh to monitor progress, but the file didn't appear until it was about 400MB. Linux 2.6 kernel, Bash 4, ...
4
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1answer
606 views

fstrim and iostat

I have a new samsung ssd in my new notebook. I tuned up everything to avoid writings in the disk (firefox profiles and /var/log in memory), I'm using a ext4 fs with relatime and I use fstrim once a ...
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1answer
151 views

Strange problem with IO or file system or what?

On a SLES 11 SP2 32-bit system I'm seeing a strange problem. It's as if the OS can not open a file from the beginning of the file. Say I have a file that is 200 lines. If I cat or more or vi the ...
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3answers
14k views

Determining Specific File Responsible for High I/O

This is a simple problem but the first time I've ever had to actually fix it: finding which specific files/inodes are the targets of the most I/O. I'd like to be able to get a general system overview, ...
2
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1answer
1k views

-bash: /usr/sbin/useradd: Input/output error — What does this mean?

Today, on my Centos server I tried to add a user but got the following error: -bash: /usr/sbin/useradd: Input/output error How do I fix it?
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2answers
383 views

How to make directory modication date change when files from that dir change?

For example, if a file has been changed in that directory, then directory modification date should be updated. Basically any changes that happen in that directory should trigger a "touch" on the ...
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0answers
2k views

find ount what [flush-8:0] is writing

Using iotop, I found out that [flush-8:0] is doing a lot of hard disk activity, which explains the annoying slowdowns. However, I can't figure out what's the actual cause behind this flushing. No ...
5
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2answers
811 views

Why do systems become slow when doing massive writes to disk?

I want to know why systems become slow when writing mass data to disk. I think that for system to become slow, there should be some issue with CPU. But write is only I/O bound. Do hardware ...
2
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0answers
205 views

Shorter timeout on I/O errors MacOS X

How do you set a shorter timeout value for read/write I/O errors on MacOSX? We tend to get a few semicrashed disks and want to rsync the contents to a secure location, but when the file subsystem ...
2
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1answer
312 views

CONFIG_GPIO_SYSFS makes /sys/class/leds disappear

I have an embedded Linux board I'm working on, with a button and a couple LEDs. By default, I can control the LEDs via /sys/class/leds/redled/brightness However, I have no way to monitor the ...
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1answer
209 views

Unable to delete a directory even as root

I am unable to delete a directory even as root. The command rm -rf kdyiyv.pif returns nothing. Then I tried the command, touch kdyiyv.pif for which there was an error: touch: setting times of ...
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4answers
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Special File that causes I/O error

I want to automatically test if a piece of software reacts as expected if an essential SQLite DB file fails to be read (causing an I/O error). Exactly that happened some days ago at a client. We ...
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3answers
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Can the “du” program be made less aggressive?

We have a regular job that does du summaries of a number of subdirectories, picking out worst offenders, and use the output to find if there are things that are rapidly rising to spot potential ...
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1answer
172 views

Determine how much a process is using each disk?

How do I tell how much load a particular process is contributing to each of several available volumes/mounts? It seems that dstat only shows aggregate stats across all processes per disk, and iotop ...
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2answers
2k views

iotop but for particular disk?

Is there a tool like iotop but for monitoring IO on specific volumes? (Or perhaps I missed a way to filter iotop?) If not is there any way to get at this information via (say)/proc? (dstat etc. ...
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1answer
8k views

I/O errors on hard disk on Linux boot

Here is a screenshot of booting Arch. I guess the reason is that I force poweroff my Arch linux many times. (I already force poweroff my Arch because my firefox flash plugin use too much memory to ...
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0answers
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How to set up ZFS with ZIL and L2ARC SSD?

I have been considering bcache and flashcache. However my friend suggested me something called ZFS. In fact it says that formating disk with ZFS can actually do the exact same thing without kernel ...
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2answers
2k views

Storing thousands of files in one directory

I have a web-site that I'm checking for performance issues and bugs, and i came across a caching code that caches thousands of files into one single directory. I understand that this is not good and ...
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3answers
1k views

Why is I/O uninterruptible?

What is the rationale behind making I/O uninterruptible? What would be the negative consequences if a process handling I/O were allowed to handle a signal?
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905 views

How to improve IO when there is a lot of random read and write?

My scripts uses tons of read and writes. Most of them are small and random. I want Linux to wait 10 seconds before writing any data to the disk. How would this be achieved? I think Linux can already ...
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1answer
521 views

Does linux have something like supercache?

I installed http://www.superspeed.com/desktop/supercache.php for windows and the result is awesome. Every program I run is faster. Basically it uses the memory to cache data. Simple idea. I also use ...
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1answer
130 views

Strange IOStat xk. Moving a mere 40GB data is too slow. Can anyone explain?

iostat -xk 5 avg-cpu: %user %nice %system %iowait %steal %idle 0.99 0.00 1.10 11.01 0.00 86.89 Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s ...
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2answers
577 views

is writing to slow storage in nohup mode blocking the process?

If I have a process writing to nohup and the storage where it writes to is slow, does it block the process which is running in nohup? For example: process A is running in nohup, it needs to write 10 ...
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1answer
159 views

IOStat report large ocassional writes but find reports no big file

root@host [/home4]# find . -type f -size +2000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }' ...
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3k views

How to know recently updated files

If I run iostat -x 1 I saw ocassionally large 5MB to 10MB writes. What files are being written? I want to check the recently created files with size over 5MB for example. How would I do so?
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1answer
380 views

iostat report huge writes to drives that's not even mounted

root@host [~]# fsck /home2 fsck from util-linux-ng 2.17.2 e2fsck 1.41.12 (17-May-2010) /dev/sdb1: clean, 6018617/91578368 files, 54524459/366284000 blocks root@host [~]# fsck /home4 fsck from ...
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1answer
4k views

Which drive had a “journal commit I/O error”?

I received a message: kernel:[123456.789012] journal commit I/O error Which disk drive had the journal error?
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2answers
198 views

Determine which process is taking most of disk bandwidth?

When the HDD indicator is blinking (for a long period), how could I know which process is taking most disk bandwidth?
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1answer
453 views

Does symlinking from Drive A to Drive B affect I/O on Drive A?

I was wondering if IO through a symbolic link affects IO on the host drive even if it points to a seperate drive? My setup is, /dev/sdb2 1.8T 443G 1.3T 26% /home1 /dev/sda3 1.8T 1.7T ...
25
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1answer
5k views

Meaning of colours in htop

Given the option: [ ] Detailed CPU time (System/IO-Wait/Hard-IRQ/Soft-IRQ/Steal/Guest) In htop (Version 1.0.1) what are the meanings of the colours? In the following image, I'm seeing rather a lot ...
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1answer
2k views

I/O error but no bad block is reported in syslog

I got errors like this in my syslog, but there's no bad block or sector defined in kernel report, I can't just replace the HDD right now and I prefer to reallocate the bad blocks for now, so I need ...
23
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2answers
10k views

Can I watch the progress of a `sync` operation?

I've copied a large file to a USB disk mounted on a Linux system with async. This returns to a command prompt relatively quickly, but when I type sync, of course, it all has to go to disk, and that ...
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3answers
14k views

How to Throttle per process I/O to a max limit?

I'm looking for a way to limit a processes disk io to a set speed limit. Ideally the program would work similar to this: $ limitio --pid 32423 --write-limit 1M Limiting process 32423 to 1 megabyte ...
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3answers
2k views

Construct a command by putting a string into a tty

I managed to do this echo -n "command" > /dev/tty1 The letters appear, and the cursor moves, but they are "ghosts" – if you hit Enter, nothing happens (they are not in stdin). Edit: In the ...
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2answers
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What is the difference between > and >> (especially as it relates to use with the cat program)? [duplicate]

Suppose that I have a file called temp.txt. Using the cat program, I would like to add the contents of this file to the end of myfile.txt -- creating myfile.txt if it does not exist and appending to ...
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2answers
1k views

What keeps one side of an rsync so busy?

I've got a Debian machine on my LAN serving as a backup server for the others. It has four HDDs combined into a software RAID 5 md device, on that an LVM, and on that btrfs. Backups are made using ...
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2answers
573 views

Running jobs in parallel on Ubuntu - I/O contention differences between Perl and Java

Apologies if this is off topic - it concerns the relative efficiencies of running I/O-heavy Perl/Java scripts in parallel on a Ubuntu system. I have written two simple versions of a file copy script ...
5
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3answers
693 views

File size of 60.0 PB is wrong. Can deleting it cause data loss?

While backing up some data (a 200 GB home directory) with rsync, I got an I/0 error for a particular file, after which rsync continued on "normally" with its backup. The problem source file showed as ...